Transducers are employed in a variety of applications for converting one form of energy into another. The forms of energy which often require conversion include electrical, mechanical, pressure, light, heat, sound, etc. It can be appreciated that transducers are necessary in most machines or equipment as it seldom happens that a machine does not operate between two or more forms of energy.
The development and manufacture of transducers have become highly competitive fields. There is a constant effort to provide transducers which are more reliable, accurate, less costly, easily manufacturable and more compact. Current to pressure transducers are among a class of transducers which requires a high degree of accuracy and reliability, while yet remaining cost effective. U.S. Pat. Nos. 3,441,053; 4,492,246; and 4,527,583 disclose sophisticated transducers, generally adapted for converting electrical input energy through an intermediate mechanical medium to control an output gas pressure. The first of the noted patents is mechanically complicated, while the two latter-identified patents are highly sophisticated and require a large number of electrical components. As is usually typical, an improvement in the reliability or accuracy of a transducer is generally accompanied by an increase in the complexity of the equipment.
Many transducers, and especially the electrical to pressure type of transducers which are utilized in hydrocarbon refineries, are required to be explosion-proof. Special precautions including highly sophisticated and costly enclosures have been adapted to render such transducers mechanically sound and sturdy to contain an internal explosion, if one should occur, and prevent the resulting fire or flame from spreading to the environment. Special attention is also given to circuit elements which can store electrical energy, such as inductors and capacitors, to reduce or eliminate the likelihood of such elements generating sparks. The explosion-proofing by encasement of a transducer of the type having a moving coil winding can be extremely difficult. Typically, it is expedient to mount the coil movable with respect to a permanent magnet, as magnets are generally much heavier and more bulky than the associated coils. In such a transducer, the electrical input is applied to the moving coil which then moves under the influence of the fixed permanent magnet. By virtue of its requirement to move in correspondence with the amount of current applied to the coil, it is extremely difficult to encase such a coil and render the entire transducer explosion-proof.
From the foregoing, it can be seen that a need exists for an improved electrical to mechanical transducer which is reliable, cost effective, accurate and easily manufacturable. An associated need exists for an explosion-proof transducer of the type having a lightweight permanent magnet and a coil winding combination, but with the winding fixed to a frame structure to thereby make explosion-proofing of the transducer much easier. Another need exists for an improved current to pressure transducer having a lightweight movable magnet with a high degree of permanent magnetization such that a smaller magnet can be employed, thereby also reducing the size and complexity of the transducer. Yet another need exists for a transducer structure which is of reduced complexity, which has few moving parts, a fast response time and which is yet accurate and reliable.